_NAME_
writeDataStructToFile

_PROTOTYPE_
int writeDataStructToFile(int fd, int intervalNumber, char dataBuffer[],
                                int bufferSize, char *pDataStruct, char *path);

_SHORT-DESCRIPTION_
Write a data struct into the proper position in its archive file

_DESCRIPTION_
writeDataStructToFile is used to write a data struct into the proper
position in its archive file. 
_
First this routine checks what has been written into the data file at the
interval where the passed data struct is to be written. If the interval is
all zeros (done at file initialization), the struct is written and a status
of 0 is returned. 
_
If the interval is found to contain data already, both the passed struct
and the one already in the file are written out to an auxiliary file (same
file name with ".overlap" suffix appended), the interval is filled with
char -1s, and a status of 1 is returned. 
_
If the interval is filled with char -1s, then the passed struct is written
to the auxiliary file and a status of 2 is returned. 
_
Finally, if the passed data struct is identical to the data already in the
interval, nothing is written, and a status of 3 is returned. 

_INPUT_
* fd is the file descriptor for the already opened-for-write data file. 
* intervalNumber is the number of the slot within the data file
where the data will be (or attempted to be) written. 
* dataBuffer is a char array of size equal to the struct to be written. 
* bufferSize is the size of the struct to be written. 
* pDataStruct is a pointer to the struct to be written. 
* The path of the data file is passed in case an "overlap" file path
needs to be constructed to write overlap data (see above.)

_OUTPUT_
* An integer status is returned. See description above for details.